1. Technical Field
The present invention relates to a semiconductor device, a measurement device and a correction method.
2. Related Art
Recently, in measurement devices such as electricity meters for measuring integral power consumption, integral power consumption is being measured for separate time band. Accompanying this trend, measurement devices incorporated with a built-in semiconductor device including an oscillator and an integrated circuit, and are capable of measuring power and time are known.
As a semiconductor device built into such a measurement device, Japanese Patent Application Laid-Open (JP-A) No. 2010-34094 discloses a circuit device in which radiation noise is reduced, by including an oscillator, and an IC chip having a circuit section that is electrically connected to the oscillator and thereby forms an oscillation circuit.
In such a circuit device, the oscillator includes plural electrodes, and the IC chip includes plural oscillator pads that correspond to the plural electrodes and are electrically connected to the circuit section. The oscillator is mounted to the face of the IC chip on which the plural oscillator pads are formed, with the plural electrodes and the plural oscillator pads facing each other and electrically connected through an Anisotropic Conductive Film (ACF).
JP-A No. 4-36814 also discloses a technology in which wiring from a quartz oscillator to a CPU is made minimum by building the quartz oscillator and the CPU into the same IC package, thereby preventing generation of noise such as reflection in the clock signal.
Meanwhile, in measurement of temperature in a meter such as an electricity meter, a temperature measurement element having a resistance value that changes according to temperature, such as a thermistor, is generally employed, and changes in resistance values of the temperature measurement element are converted into changes in voltage to measure the temperature. It is possible for measurement errors to arise from various causes in temperature measurement performed by the temperature measurement element. Causes of measurement error include, for example, variation in the characteristics of the temperature measurement elements (the change in resistance value with temperature), errors in converting changes in the resistance value of the temperature measurement element to changes in voltage, errors arising from fluctuations in power supply voltage supplied to a temperature measurement circuit, errors arising in AD conversion of a detection signal of the temperature measurement element, and errors arising in conversion of a digital signal into a temperature value by a controller.
In this regard, JP-A No. 2008-14774 discloses a temperature measurement device as such technology for performing temperature measurement good precision irrespective of the power supply voltage. This temperature measurement device performs correction using a linear approximation of plural points of temperature data. The temperature measurement apparatus measures temperature after a power supply voltage is applied, outputs a first voltage including temperature data and power supply voltage data, and a second voltage including power supply voltage data from which the temperature data has been removed, and determines a temperature measurement value by subtracting the second voltage data from the first voltage data.
Normally, a measurement device that is installed outside, such as an electricity meter or a gas meter, is readily affected by the ambient temperature. Further, an oscillator such as a quartz oscillator mounted to a semiconductor device as disclosed in JP-A No. 2010-34094 and JP-A No. 4-36814 has a high temperature dependency, and there are large differences in error amounts in oscillation frequency of the oscillator (referred to below as “frequency errors”) due to individual differences between the quartz crystals employed, and variation between individual devices are likely to be exist. Hence, it is desirable to correct for oscillator frequency errors due to temperature in case of mounting a semiconductor device that includes an oscillator in a measurement device that is installed outdoor.
Conventional semiconductor devices that have a timing function generally include an oscillator, a drive circuit for driving the oscillator, and a timing circuit that performs timing with a clock obtained from the oscillator. Since the drive circuit of the oscillator is built into the oscillator or to the timing circuit, at least two additional components are required for configuring the semiconductor device.
For the timing function there is a requirement of providing an accurate cycle, a correction circuit is generally built into the timing circuit in order to correct the oscillation frequency of the oscillator. However, in cases in which individual differences arise during manufacture and the oscillation frequency of the oscillator is not uniform, individual adjustment must be performed for each oscillator in the timing circuit. Namely, such cases are extremely inefficient since adjustment is necessary in the final product.
For example, as illustrated in FIG. 30, in a conventional semiconductor device, an oscillator of a predetermined frequency (for example 32.768 kHz) is connected in series to an XT0 terminal and an XT1 terminal. Load capacitors (CGL and CDL) are connected respectively to the XT0 terminal and the XT1 terminal, and across a power supply voltage Vss. The timing circuit has a correction function.
It is possible to perform correction of frequency error in such a semiconductor device if it at least has the configuration as described above. However, in cases in which the peripheral temperature fluctuates in the environment of use, correction can be performed more accurately by verifying the frequency each time of the fluctuation, and connecting a temperature sensor to obtain temperature data from the temperature sensor.
In cases of employing a temperature sensor in the semiconductor device as illustrated in FIG. 30 in order to perform oscillation frequency correction of the oscillator accompanying fluctuations in external temperature, mounting of the temperature sensor is required which results in additional manufacturing cost. Moreover, depending on the arrangement of the temperature sensor, there is no guarantee that the peripheral temperature of the oscillator and the temperature obtained by the temperature sensor match.
The semiconductor device illustrated in FIG. 31 incorporates a temperature sensor, which is externally affixed in the semiconductor device illustrated in FIG. 30, so as to achieve reduction in the number of peripheral components and costs. However, in cases in which a temperature sensor is built into a semiconductor, since complete heat dissipation is not achieved in a packaged semiconductor (see FIG. 32), there is a possibility of a difference arising between peripheral temperature and the surface temperature of the semiconductor chip, as same as the cases of externally fixing a temperature sensor.
A common issue in the conventional semiconductor devices illustrated in FIG. 30 and FIG. 31 is that since the oscillator and the oscillator load capacitance are affixed externally, this becomes a constraint to downsizing the board in its final product. Additionally, since a quartz oscillator operates with a minute voltage and current, and thus susceptible to noise or leak current, there is a constraint that the quartz oscillator needs to be provided in the vicinity of a timing circuit. Further, correction operation in the final product is still required since the semiconductor device and the oscillator are separately supplied.
As described above, in a semiconductor device with a timing function, since the oscillator such as a quartz oscillator has temperature dependency, the temperature of the oscillator needs to be measured in order to perform correction of the oscillation frequency of the oscillator. In cases in which the temperature sensor is disposed in the vicinity of the oscillator in order to correct the oscillation frequency of the oscillator, data of the temperature sensor needs to be input to the correction circuit. In order to perform correction using the temperature of the correction circuit at good precision, there is a concern that constraints might arise regarding the layout, such as disposing the oscillator in the vicinity of the correction circuit. If an expensive high precision oscillator is employed in order to eliminate the need for correction, there is a concern regarding a rise in manufacturing costs.